1. Field of the Invention
This invention relates to an improved sash lock for double hung windows which self centers the sashes and substantially limits the movement of the sashes with respect to one another.
2. Description of Related Art
Sash locks for double hung windows are well known. Double hung windows are generally defined as two individual glass panels, each panel in a separate sash, with the two sashes moveable in a vertical plane. The sashes are mounted in a window frame, defined by jamb liners on the side, a head jamb on the top and a sill on the bottom. Typically, the sashes are counter-balanced by weights or balances, which provide for easier vertical movement of the sashes.
The sash is comprised of a top rail, side stiles and a bottom rail. Further, the bottom rail of the top sash is also called the upper check rail and the top rail of the bottom sash is called the lower check rail. The check rails are adjacent to one another when the sashes are locked and pass one another when the sashes are operated.
In order to prevent vertical movement of the sashes, locking mechanisms are placed on the check rails. The locking mechanisms typically have a latching portion and a keeper portion. The latching portion generally rotates and engages the keeper portion, thus preventing vertical movement of the sashes. Prior patents showing a variety of different sash locks include U.S. Pat. Nos. 110,733; 112,717; 126,754; 197,848; 564,426; 1,122,026; 2,422,723; 3,645,573, and 3,811,718.
In recent years, a new type of double hung window has been introduced, such as that marketed by Andersen Corporation commercially available under the trademark "D.C. Window." This new type of window allows the user to clean the outer surface of the window in an easy manner. The window has flexible side jamb liners such that the sash may be pulled inwardly, out of the side jamb liners, and positioned so that the window may be easily cleaned. Thereafter, the sash is pushed back into the side jamb liners and thus positioned in its operational mode.
A problem of prior sash locks is even after the sashes were locked, there was still movement of the sashes with respect to one another. This movement occurred in all directions, with the greatest movement often occurring in a lateral plane, resulting in a side to side movement of the sashes. Such movement is undesirable for numerous reasons. One problem encountered from such movement is the sashes would not fit correctly within the frame, thus resulting in air, moisture and wind leaks. Another problem encountered is safety. If the sashes were not tightly fit together, with minimal clearance or tolerance between the sashes, it is easier to force a wire or other instrument through the space and open the sash lock from the outside, thus allowing an intruder access to the dwelling. These problems have been accentuated with the advent of the tilt windows described above. As a result of the side jamb liners being flexible, the sashes can move even more than the sashes of ordinary double hung windows within the window frame. This has serious repercussions as to the weatherability and the safety of the windows. Thus there exists a need for a sash lock which limits movement of the sashes and provides for proper alignment of the sashes. There also exists a need for a sash lock which can be more easily and cost effectively manufactured.